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Date List Generator

Generate an exact inclusive sequence of up to 10,000 calendar dates with a chosen day step and optional weekday labels.

Privacy: your files never leave your device. All processing happens locally in your browser.

How to use

  1. 1.Choose valid start and end dates, keeping the end the same as or later than the start.
  2. 2.Enter a whole-number day step, optionally add weekday names, and generate the complete sequence.
  3. 3.Check whether the step landed on the end date, then copy the one-per-line output for your workflow.

About Date List Generator

Date List Generator creates a chronological sequence between two calendar dates. Enter a start date, an end date, and a whole-number step measured in days. A step of one lists every eligible date, seven creates a weekly sequence, and a larger value creates a regular custom interval. Both endpoints are eligible. The end date appears only when the chosen step lands exactly on it, and the summary states whether that happened. You can add English weekday names, review the complete one-per-line result, and copy the text into a spreadsheet, schedule draft, test fixture, content plan, or another local tool.

The tool treats every entry as a calendar date rather than a timestamp. It uses the timezone-free proleptic Gregorian calendar, the same calendar model used for HTML date values and ISO calendar dates. There is no midnight, UTC offset, daylight-saving transition, locale-dependent parser, or conversion through a Unix timestamp. That distinction prevents a date from moving backward or forward when a browser runs in another time zone. The accepted shape is strict four-digit year, two-digit month, and two-digit day: YYYY-MM-DD. Supported years run from 0001 through 9999.

Date validation follows the real length of each month. January has 31 days, April has 30, and February has either 28 or 29. A year divisible by four is a leap year unless it is divisible by 100; a year divisible by 400 remains a leap year. Consequently, 2000-02-29 is valid while 1900-02-29 is not. Invalid month numbers, impossible days, incomplete fields, and an end before the start reject the request. The generator never relies on a browser silently normalizing an impossible date such as April 31 into May.

The interval is an integer from 1 through 366 days. It is applied from the original start, not repeatedly rounded to a month boundary. Starting on January 30 with a two-day step produces January 30, February 1, February 3, and so on. A seven-day step preserves the weekday because a Gregorian week has seven consecutive calendar days. The tool does not offer month or year steps because those units require a separate overflow policy for dates such as January 31 or February 29. Use Date Add Subtract Calculator when the task is calendar-month or calendar-year arithmetic.

Generation is deterministic and complete within its stated budget. Before building output, the browser converts each valid endpoint to an integer calendar-day ordinal and calculates the exact result count. Up to 10,000 dates are accepted. A request for 10,001 or more fails with the calculated count and returns no partial list. The tool does not keep only the first page, insert an ellipsis, skip weekends, remove holidays, sample rows, or infer working days. The ordinal is converted back into an independently validated Gregorian year, month, and day for every output line.

Optional weekday labels are derived from the same ordinal, with Monday as the first ISO weekday. They are fixed English names rather than localized browser strings, so identical inputs produce identical copyable output on every device. Adding weekday names changes only the displayed line, not the sequence. The result remains plain text. Copying requests clipboard access only after the button is pressed. If permission is denied, the visible read-only text area can still be selected manually.

This generator is not an appointment scheduler, business-day calculator, holiday calendar, recurrence engine, or time-zone converter. It does not know opening hours, market sessions, religious calendars, school calendars, regional holidays, leap seconds, or a user's location. A daily list is not proof that every listed day is available or operational. Review the sequence against the rules of the destination system before importing it, especially when deadlines, payroll, travel, finance, or legal obligations are involved.

All parsing, counting, weekday calculation, formatting, and copying run in the current browser tab. No date range is uploaded or stored by the widget. Standards-based golden tests cover ordinary and century leap years, 30-day and year boundaries, a multi-day step across February, the minimum supported date, weekday anchors, invalid dates, the 10,000-row boundary, and a step that stops before the end. Those checks make the calendar contract auditable while keeping the tool focused on one simple job: producing a transparent list of dates.

Methodology & sources

Accept strict YYYY-MM-DD endpoints with four-digit years 0001 through 9999. Validate proleptic-Gregorian month lengths using the divisible-by-4, except-divisible-by-100, unless-divisible-by-400 leap-year rule. Convert a valid date to a one-based ordinal using completed years, fixed month offsets, and the leap-day adjustment. Reject a descending range or a non-integer step outside 1 through 366. Compute floor((endOrdinal-startOrdinal)/step)+1 before allocation and reject counts above 10,000 without partial output. Convert each selected ordinal back by binary-searching its year and subtracting month lengths, then format strict YYYY-MM-DD. Optional weekday names use (ordinal-1) modulo 7 with 0001-01-01 as Monday. Tests use eight independent standards-derived golden ranges plus invalid, round-trip, weekday, alignment, and exact result-budget boundaries.

Frequently asked questions

Are the start and end dates included?
The start is always included. The end is included only when the chosen whole-day step lands on it exactly; the result summary reports that condition.
Does daylight saving time change the list?
No. The tool uses timezone-free Gregorian calendar dates rather than timestamps, so UTC offsets and daylight-saving transitions cannot shift an output day.
Can this generator skip weekends or holidays?
No. It applies a fixed number of calendar days and has no location or holiday dataset. Review or filter the output separately when business-day rules matter.

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